Timebase vibrator assembly

ABSTRACT

In a timebase mechanical vibrator having three parallel oscillating arms arranged in a common plane wherein the central arm oscillates in opposite phase to the two outer arms, the width of the central arm is 2a/n when the width of each outer arm is a and n is a positive integer greater than unity. A sensing magnet is mounted on the free end of one of the outer arms and a driving magnet is mounted on the free end of the other outer arm. A feed magnet is mounted on the free end of the central arm in magnetic cooperation with a rotatable gear wheel to intermittently advance the gear wheel.

United States Patent Hatsuse et al.

TIMEBASE VIBRATOR ASSEMBLY lnventors: Toshikazu Hatsuse; Hiromi Ueda; Shouiti Ozawa; Yuh Yasuda, all of Tokyo, Japan Assignee: Citizen Watch Company Limited,

Tokyo, Japan Filed: March 26 1971 Appl. No.: 128,298

Foreign Application Prlority'Data Field of Search ..310/15, 20, 21, 22, 103, 23, 310/24; 58/23, 23 D, 234 F, 23 V, 116, 78; 331/116; 318/123-132 [451 Oct. 17, 1972 [56] References Cited UNITED STATES PATENTS 3,462,939 8/1969 Tahaka et a1. ..58/23 2,690,646 10/1954 Clifford ..58/1 16 Primary Examiner-D. F. Duggan Attorney-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT In a timebase mechanical vibrator having three parallel oscillating arms arranged in a common plane wherein the central arm oscillates in opposite phase to the two outer arms, the width of the central arm is 2a/n when the width of each outer arm is a and n is a positive integer greater than unity. A sensing magnet is mounted on the free end of one of the outer arms and a driving magnet is mounted on the free end of the other outer arm. A feed magnet is mounted on the free end of the central arm in magnetic cooperation with a rotatable gear wheel to intermittently advance the gear wheel.

2 Claims, 11 Drawing Figures PATENIEDMI 17 i972 SHEET 1 (IF 2 v FIG-2 "FIG.

' *PRIOR ART 1b 1c -FlG- 4 F65 PATENTED 17 3,699,412 sum 2 or 2 l TIMEBASE VIBRATOR ASSEMBLY This invention relates to improvements in and relating to a timebase vibrator assembly having three parallel oscillatory arms and especially adapted for magnetic cooperation with a magnetic wheel for rotatingly driving the time-keeping gear train in a timepiece.

The commonly known mechanical vibrator of the above kind has been generally so designed that the both outer arms thereof are connected at their tip ends by a lateral member which carries afeed magnet cooperating magnetically with the magnetic wheel, while the central arm is provided with a sensing magnet as well as a drive magnet which are adapted for electromagnetically cooperating respectively with sensing coil means and drive coil means mounted stationary and electrically connected with a combined electronic sensing and drive circuit means positioned within the inside space of the timepiece.

Therefore, the feed magnet and the sensing and drive magnets are so-to-speak crossed with each other, thereby representing a rather complicated structure of the vibrator assembly, in addition thereto, inviting a rather high value of power consumption.

The object of the present invention is to provide an improved timebase vibrator assembly, obviating substantially the aforementioned conventional drawbacks.

This and further objects, features and advantages of the invention will become more apparent when read the following detailed description of theinvention by reference to the accompanying drawings, illustrative of a conventional comparative vibrator assembly and several preferred embodiments of the invention.

In the drawings:

FIG. 1 is a plan view of substantial part of a mechanical vibrator belonging to prior art.

FIG. 2 is a similar view to FIG. 1, illustrative, however, the first embodiment of the invention.

FIG. 3 is an enlarged and more specifically shown perspective view of a practical vibrator assembly cooperating with a magnetic wheel, wherein the vibrator per se is same as shown in FIG. 2.

FIG. 3A is a part of the mechanical vibrator shown in FIG. 3.

FIG. 4 is a schematic perspective view, illustrative of the principle of working mode of a torsional vibration system. b

FIG. 5 is a plan view of the practical vibrator shown in FIG. 3.

FIGS. 6 and 7 are charts for the illustration of the improved isochronism with the invention.

FIGS. 8 10 are a top plan view, a side view and an end view of a slightly modified mechanical vibrator shown in FIG. 5.

Before entering into the detailed description of the invention a comparative conventional mechanical timepiece vibrator proper will be described briefly by way of example and by reference to FIG. 1.

FIG. 1 shows a three arm conventional vibrator generally shown at l and having a base portion 1a and three parallel vibratory arms lb, 10 and lb made integral therewith. Arms lb and lb are positioned at the both outsides of the said vibrator and that shown at 1c is positioned at the center thereof relative to the outer arms lb and lb. Although not specifically shown, all these vibratory arms have a common and specifically selected constant thickness which can be denoted by h. The effective length of these arms is also constant which is denoted by 1" in FIG. 1. The outer arms lb and lb' have a certain constant width denoted by a, while the central arm 10 has a doubled width 2a as shown. The outer arms vibrate in unison with each other in their amplitude and phase, while the central arm 1c vibrates in opposite phase to the outer arms, as a preferred and most advantageous mode of the operation.

It will be seen from the foregoing that the vibratory amplitude of the outer arms is same as that of the central arm.

In the, improved mechanical vibrator shown generally at 10in FIG. 2, showing again a three parallel arm type one, having outer arms 10b and 10b and a central arm 10c arranged parallel one after another and made integral with the base portion at 100. The effective lengths of these vibratory arms are selected commonly to a certain definite common length 1" as shown; the width of each of the outer arms is selected to a common one denoted a as before. The thickness of all the arms is selected to a certain definite and common value which may be expressed by h" although not specifically shown. In the embodiment shown, the width of the central arm 10c is selected to a rather reduced value 2a/n, n being a positive integer larger than unity.

Now assuming that the amplitude of vibration of the outer arms be A;" the equivalent mass thereof be M,; and the equivalent spring constant be k,," respectively; and that those of the central arm be A M and k respectively, then we will obtain the following formulas:

The vibrators shown in FIGS. 1 and 2 are intended to cooperate with a rotatably mounted magnetic wheel such as shown at 22 shown in FIG. 3. The aforementioned amplitude A is assumed enough to feed the magnetic wheel, as will be more specifically described hereinafter by reference to FIG. 3. It is further assumed that the kinetic energy owned by the regularly vibrating conventional vibrator 1 be E and that of the improved vibrator 10 be E so we will obtain the following forwherein m= k /M, V kg/Mz which means the natural frequency of the respective mechanical vibrator.

Since n is larger than unity,

as observed clearly by the comparison of the formula (4) with (5).

In addition thereto and as ascertained by our practical experiments, the resonance sharpness Q of the improved vibrator is at least similar to that of the conventional one and frequently improved thereover.

It will be seen therefore from the foregoing that with use of the improved mechanical vibrator, the power consumption can be substantially improved over the conventional one.

In the foregoing description, the attached vibratory masses to the tip ends of the vibratory arms have been intentio'nary omitted from consideration in order to more sharply define the main feature and nature of the invention, but, in practice, these masses must naturally be taken into account. It has been ascertained by prac- Jical experiments that by proper selection of the mass values and also their distribution so as to satisfy the formula (2), the desired effect can be easily attained as theoretically supposed from the foregoing substantially mathematically given disclosures.

In the practical arrangement shown in FIG. 3, the mechanical vibrator is so mounted that it feeds magnetically the magnetic wheel 22 was referred to briefly hereinbefore. In this embodiment, n is selected to 2. Base portion, outer arms and central arm of the vibrator 10 are denoted with 10a, 10b, 10b and 100, respectively as before. Although in FIG. 2', the base portion 10a has been shown in a simplified schematic way, the

practical base portion, equally denoted with 10a, is

provided with a pair of connecting strip parts 14 and 15 bridging the base portion proper and a common lateral root portion 11 from which the effective lengths of the vibrator arms extend.

The base portion 1a is formed with two separated openings 16 for insertion of set screws, not shown, by which the mechanical vibrator 10 is fixed rigidly at its root portion onto a stationary member, preferably the conventional lower plate, not shown, of the timepiece movement, not shown, fitted with the vibrator accordin g to this invention, adapted for magnetic cooperation with the magnetic wheel 22.

Outer vibrator arms 10b and 10b are fitted rigidly at their respective tip ends with cylindrical permanent magnets 17 and 18, respectively, by means of glue agent or the like conventional fixing means. The polarities of these magnets 17 and 18 are clearly shown in FIG. 3A. Magnet 17 serves in this specific embodiment as sensing one, while magnet 18 serves as drive one.

Stationary sensing coil 20 and drive coil 21 schematically shown are arranged to cooperate, as known per se, with the sensing and drive magnets 17 and 18, respectively. Although not shown, these coils 20 and 21 are rigidly mounted on the said lower plate, not shown on account of its very popularity.

The central vibratory arm 100 is provided at its free end with a feed magnet shaped into a substantially channel arranged on a vertical plane and formed with an air gap 19a, so as to magnetically cooperate with the magnetic wheel 22 having peripheral teeth 22a and inwardly positioned and radially arranged perforations 22b as known per se. These teeth 22a are adapted for driving the conventional time-keeping and indicating gear train, although not shown. The perforations are arranged for establishing a magnetically cooperating with the feed magnet 19, so as to be driven therefrom intermittently for keeping the time-keeping rotational movement of the wheel For this purpose, this wheel 22 is rotatably mounted as'kn'own per se on the lower plate of the timepiece. The feed magnet 19 oscillates with a specific amplitude which is double the oscillating amplitude of the outer arms 10b and 10b. If the positive integer rt is 3, the amplitude will increase to three times the oscillation amplitude of the outer arms 10b and 10b, and so on. The amplitude of the feed magnet 19 is so choosen that it can feed the wheel 22 in its rotational sense, which means that the oscillation range of the gap 19a well covers the perforation 22b when seen in the vertical plane in which the feed magnet oscillates. By adopting the aforementioned structure, it does not need to use a uniting member rigidly connecting the tip ends of the outer oscillatory arms 10b and 10b. Sensing coil 20 and drive coil 21 are electrically connected with a conventional electronic sensing and drive circuit 23 as shown in FIG. 3. In this embodiment, the

circuit 23 has been shown in its basic and simplest form, having a transistor 24, a battery 24, a resistor 26 and a capacitor 27 which are electrically connected one after another as shown. But, the circuit may be of more complicated arrangement having two or more transistors and more numerous auxiliary circuit components such as resistors and condensers, as is commonly known among those skilled in the art.

The abolition of the lateral connector connecting the tip ends of the outer oscillatory arms will provide a more easy assembling convenience, as well as a substantially reduced power consumption which may be invited by reducing the mass weight of the oscillation masses attached to the free ends of vibratory arms, thanks to the said abolition.

In a preferred modification not specifically shown, the center of gravity of the outer masses 17 and 18 is coincides in its position with that of the central or feed magnet mass 19, when seen in the neutral or nonvibrating state of the vibrator 10. In addition, the length of the vibratory arms can be extended as desired, so as to improve the time-stepping operation of the timepiece movement.

In FIG. 4, a torsional vibration system is'shown only in a simplified way. In this figure, 0 and n0 represent torsionally oscillating angles of a first and a second oscillation mass P and Q which are rigidly connecting by an elongated torsion spring R. A represents a nodal point of this oscillation system. The nordal point A is positioned on a point which divides the overall length l of the bar R at a specific ratio of l n as shown. It is commonly known, a most favorable result is obtained by placing the supporting point of the system at the nordal point. By adopting such measure, inevitable vibration losses can be reduced to a possible minimum.

In the vibrator shown in FIG. 5 which corresponds to that shown in FIGS. 3 and 3A, the nodal lines which represent between the bending oscillation range and the torsional oscillation range are shown by several dotted lines. It will be seen that optimum position of connecting strips 14 and 15 depends upon the practical widths of the oscillatory arms 10b, 10b and 100. The lateral length L, of the torsionally oscillating part depends naturally upon the arm'widths. This length L, is established by drawing a lateral or horizontal line from the cross point of two crossing nodal lines relative to the central oscillatory arm 10c, until it crosses with the inclines nodal line relative tothe left-hand arm 10b. The width of the root portion or yoke 11 is represented by b in FIG. 5.

Assuming that the width of the central arm is equal to 2a/n as before, and the amplitude of the outer arm be A, and that of the central arm be Ag, then:

where, L represents the length between the points c and d shown in FIG. 5, the point d being the nodal point.

We have ascertained from our practical experiment that the above relations are correct also in practice. We have further ascertained that by positioning the connection strips 14 and 15, so as to satisfy the above relations, an improved frequency stability, resonance sharpness and high operating efficiency of the mechanical vibrator of the above kind can be realized.

The aforementioned mathematical relationship can be modified into the following formula:

L x 2/3 when n be 2.

In FIG. 7, a diagram is shown, so as to clarify the isochronism-improvement characteristics plotted the frequency variation against the voltage variation. In the conventional art, the isochronism is correctingly adjusted by altering the position of a channel-sectioned magnetic corrector, not shown, mechanically towards or remote from the feed magnet. By properly adjusting the position of the magnetic corrector relative to the feed magnet, the characteristic curve may be adjusted to (a) to (b), the latter representing a more superior irochronism.

According to the present invention, the conventional magnetic corrector can be abolished without hindrance. in fact, a more favorable or more flat characteristic curve (b') as shown in FIG. 6 can be obtained, so as to avoid substantially off-set characteristics shown at (a) and (b'). The curve (a) corresponds in FIG. 6 corresponds to that shown at (a) in FIG. 7. The curve (c') represents a similar curve which has been obtained with a conventional type three arm vibrator wherein the tip ends of the outer arms have been mechanically conjointed together by means of a lateral connector.

Finally, referring to FIGS. 8-10, a more practical embodiment from the foregoing is described briefly hereinbelow. In this embodiment, each of the numerals is shown as the corresponding same reference numerals as employed in the first embodiment regardless of possible minor difference in its configuration so far as it can performs similar function as before, yet each reference numerals being, however, added with 100 for specific identification from the foregoing. It should be noted that the figure shown in FIG. 10 is, more correctly to say, of partial section.

Sensing and drive magnets 117 and 118 are fixedly attached to their respective mounting members 117' glueing or the like or any combination thereof which are spot welded to the oscillative arms ll0b' and 110b, respectively, as schematically hinted by small dotted line circles 117" and 118". Feed magnet 119 is also fixedly attached to its mounting strip 119 as before which is spot-welded again onto the free end of the central arm 1100 at 119". In this case, the effective length of the oscillatory arm must include a corresponding one of each related magnet support strip. As will be easily seen, the operation of the present embodiment is practically same as before; thus no further an analysis will be set forth for better understandin f the 'nve tion.

From th oregoing, i t will be easily seen that any one of the structural or functional feature shown and described relative to one embodiment can be, when possible within the framework of the invention, employed in other embodiment of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are as follows:

1. A mechanical vibrator for use as a time base in a timepiece comprising three parallel substantially equal length oscillatory arms arranged in spaced-apart relaand 118 by pressfitting,

. tion in a common plane and provided with a common base portion adjacent one end thereof, feed magnet means mounted on the free end of the central arm for cooperation with a magnet wheel for stepwise feeding of said wheel in response to the oscillative movement of the central arm in opposition to the oscillative movement of the two outer arms, sensing magnet means mounted on the free end of one of the two outer arms and drive magnet means mounted on the free end of the other of the two outer arms; said sensing and drive magnet means being arranged for cooperation with stationary sensing and drive coil means respectively, the center of gravity of the feed magnet means being positioned substantially in coincidence with that of the imaginary combined mass of said sensing and drive magnet means, the ratio between the sum of the widths of the two outer oscillatory arms and the width of the central oscillatory arm being selected as n:l wherein n is a positive integer, and said sensing and drive magnet means being arranged relative to said feed magnet means with their magnetic poles in a close but opposing relation to provide a magnetic attraction therebetween which is maximum when said vibrator is disposed in its planar condition.

2. A vibrator as set forth in claim 1 further comprising intermediate mounting means disposed between each of said magnet means and its related oscillatory arm. 

1. A mechanical vibrator for use as a time base in a timepiece comprising three parallel substantially equal length oscillatory arms arranged in spaced-apart relation in a common plane and provided with a common base portion adjacent one end thereof, feed magnet means mounted on the free end of the central arm for cooperation with a magnet wheel for stepwise feeding of said wheel in response to the oscillative movement of the central arm in opposition to the oscillative movement of the two outer arms, sensing magnet means mounted on the free end of one of the two outer arms and drive magnet means mounted on the free end of the other of the two outer arms; said sensing and drive magnet means being arranged for cooperation with stationary sensing and drive coil means respectively, the center of gravity of the feed magnet means being positioned substantially in coincidence with that of the imaginary combined mass of said sensing And drive magnet means, the ratio between the sum of the widths of the two outer oscillatory arms and the width of the central oscillatory arm being selected as n:1 wherein n is a positive integer, and said sensing and drive magnet means being arranged relative to said feed magnet means with their magnetic poles in a close but opposing relation to provide a magnetic attraction therebetween which is maximum when said vibrator is disposed in its planar condition.
 2. A vibrator as set forth in claim 1 further comprising intermediate mounting means disposed between each of said magnet means and its related oscillatory arm. 